1. Field of the Invention
The present invention relates to cassettes for holding electrophoretic gels and, more particularly, to cassettes for electrophoretic gels formed of two parts which incorporate means to hold the two parts of the cassette together.
2. Background Art
Electrophoretic gels are gels, usually of polyacrylamide, which are used for the separation of proteins and other macromolecular compounds. The material to be separated is placed at one end of the gel and a direct electrical field is applied between the ends of the gel causing the molecules to migrate through the gel at rates dependant upon the molecular size of the compound.
Electrophoretic gels have been traditionally sold sandwiched between a pair of sheets of glass. The sheets of glass are held in an appropriate parallel spaced relationship by a pair of spacers positioned down each side of the gel. A mixture of compounds to be separated is normally introduced into one of a number of small wells formed in an upper edge of the gel before the direct current field is applied to the gel. It is usual to run a number of such mixtures simultaneously on an electrophoretic gel in a side by side arrangement. For this purpose one mixture is placed in each of a series of wells formed in the upper edge of the gel. The wells in the upper edge of the gel are usually formed by pushing a comb into the upper edge of the gel to form the wells at the time the gel is to be used or a series of small tubes are pushed into the upper edge of the gel and themselves form the wells.
The use of glass in forming the cassette has had the advantage of rigidity, good gel adhesion, chemical compatibility with the gel and good heat conductivity. It has had the disadvantage of high production cost for a disposable item and the relatively ungainly methods for forming the wells as has been described above. It has been suggested previously to form a cassette from a synthetic plastics material, however, these proposals have not been successful for a number of reasons. It proved difficult to form the walls of the cassette with sufficient rigidity while still being sufficiently thin for good heat transfer and ease of manufacture. There has also been a problem in ensuring sufficient adhesion of the gel to the plastics material. In the absence of good adhesion the gel is liable to slip out of the cassette during electrophoresis. Some plastics materials have also been found to inhibit polymerization of the gel monomer solutions flowed into the cassette during formation of the gel.